Apparatus for both single and double injection molding

ABSTRACT

Single and double injection molding using a single molding machine is made possible by providing two injection units, each having an injection nozzle, and a stationary platen three insertion holes into which the nozzles can fit. For double injection, the injection units are moved transversely of the stationary platen so as to orient both injection nozzles with a respective one of the insertion holes. For single injection, the injection units again are moved transversely of the stationary platen so as to orient one of the injection nozzles with one of the insertion holes, with the other nozzle not being so oriented.

This is a divisional of application Ser. No. 07/655,497 filed Feb. 14,1991 now U.S. Pat. No. 5,183,621.

BACKGROUND OF THE INVENTION

The present invention relates to a method of double injection moldingand to a machine therefor, in which both single injection molding anddouble injection molding can be performed by the same machine.

One known two-color injection molding machine includes two injectionunits by which two molten synthetic resins are injected sequentiallyinto dies tightened on each other by a single clamping unit and having asingle gate.

To manufacture separately two molded products from different material orhaving two different colors, the products are molded by two moldingmachines.

Since the two-color injection molding machine does not include a unitfor moving the two injection units transversely in the direction of thewidth of the bed of the machine, the machine can be used only for thedies having the corresponding gate position, but cannot used for otherdies which are positioned differently. For that reason, the machine hasa limited range of utility, thus increasing the cost of the equipment.

Where two molded products, having different colors or being made ofdifferent materials, are manufactured separately by two moldingmachines, there is a problem in that the cost of control of the numberof the manufactured products and the cost of the equipment are high.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a method of double injection molding and a machine therefor, inwhich single injection molding also can be performed. A single clampingunit and two injection units are prepared so that double injectionmolding can be performed by using both of the injection units and dieswhich have two lateral gates, and by which molded products can bemanufactured separately. Single injection molding can be performed byusing one of the injection units and dies having a single central gate.

In the double injection molding method provided in accordance with thepresent invention, a unit is moved transversely parallel to a stationaryplaten having three nozzle insertion holes at equal intervals in a rowhorizontally, so that the two injection units provided parallel to eachother on support members which are part of the transverse moving unitare moved and positioned in a double molding position, in which thenozzles of the injection units are oriented to the two lateral nozzleinsertion holes; double injection molding is performed thereafter; thetransverse moving unit is moved transversely parallel to the stationaryplaten so that the injection units are moved and positioned in a singleinjection molding position in which the nozzle of one of the injectionunits is oriented to the central nozzle insertion hole; and singleinjection molding is performed thereafter.

The double injection molding machine provided in accordance with thepresent invention includes the three nozzle insertion holes provided inthe stationary platen of the clamping unit so that the holes are locatedat the equal intervals in the horizontal row; the transverse moving unitwhich is transversely moved in parallel with the stationary platen; thetwo injection units provided parallel to each other on the supportmembers provided on the transverse moving unit; drive means provided forthe transverse moving unit so as to move the unit to the doubleinjection molding position, in which the nozzles of the injection unitsare oriented to the two lateral nozzle insertion holes, or to the singleinjection molding position, in which the nozzle of one of the injectionunits is oriented to the central nozzle insertion hole; and apositioning mechanism provided for the transverse moving unit so as toposition it in either of the double and the single injection moldingpositions.

According to a particularly preferred embodiment, the support membersare constituted by two swing bearers provided parallel to each other ona swing plate which is coupled pivotally to the transverse moving unit,thus yielding superior operation.

In each of the method and the machine which are provided in accordancewith the present invention, the two injection units are moved back onthe support members so that a prescribed distance is set between thestationary platen and the tip of each of the nozzles of the injectionunits. The transverse moving unit then is translated or movedtransversely back or forth in the direction of the width of the bed ofthe machine, so that the injection units are moved and positioned in thedouble injection molding position, in which the nozzles of the injectionunits are oriented to the two lateral nozzle insertion holes of thestationary platen. Thereafter, the injection units are moved forth sothat the nozzles thereof are inserted into the two lateral nozzleinsertion holes. After that, molten synthetic resins are injected fromthe two injection units into the dies so that the double injectionmolding is performed.

When single injection molding is to be performed, the transverse movingunit is moved transversely as the two injection units remain moved backon the support members, so that one of the injection units is moved andpositioned in the single injection molding position in which the nozzleof the positioned injection unit is oriented to the central nozzleinsertion hole of the stationary platen. The positioned injection unitthen is moved forward so that the nozzle thereof is inserted into thecentral nozzle insertion hole. After that, a molten synthetic resin isinjected from the forwardly-moved injection unit into the dies toperform single injection molding. During single injection molding, theother injection unit is located in a lateral position in the directionof the width of the bed, and so is not used for molding. For thatreason, the unused injection unit can be subjected to purging, automaticflushing or the like during the single injection molding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway plan view of a double injection molding machineaccording to one embodiment of the present invention;

FIG. 2 is a side view of the machine;

FIG. 3 is a perspective exploded view of a main part of the machine;

FIG. 4 is a perspective exploded view of the positioning mechanism ofthe machine; and

FIG. 5 is a plan view indicating the molding positions of the machineand the positions of the injection units thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIGS. 1 and 2, a stationary platen 5 of a clamping unit (notcompletely shown in the drawings) is provided on the front portion(which is the left-hand portion in FIGS. 1 and 2) of a bed 1 of aninjection molding machine which is one of the embodiments. The upperportion of the bed 1 has a front guide groove 8 and a rear guide groove8' (which are located at the right-hand side of the secured plate 5 inFIG. 1) and extend parallel to each other in the direction of the widthof the bed. A front slider 7 is fitted slidably in the front guidegroove 8, and a rear slider 7' is fitted slidably in the rear guidegroove 8'. A swing plate 2 is provided on the front and rear sliders 7and 7', and is coupled pivotally to the rear slider by a pivot pin 6projecting from the slider, so that the swing plate can be swung aboutthe pin by a fluid pressure cylinder 15 provided in an appropriateplace. The swing of the swing plate 2 ranges from one of the one-dotchain lines shown in FIG. 1 to the other.

Two swing bearers 3a and 3b are secured to the top of the swing plate 2and extend parallel to each other. A first injection unit 4a is providedon the swing bearer 3a so that the injection unit can be slid back andforth by an appropriate device. A second injection unit 4b is providedon the other swing bearer 3b so that the injection unit can be slid backand forth by another appropriate device.

A driver for moving the moving unit of the injection molding machinetransversely is constituted as now will be described. As shown in FIG.3, the front and the rear sliders 7 and 7' have screw shaft holes 7a and7b into which front and rear screw shafts 9 and 9' are screwedrespectively. One end of each of the front and the rear screw shafts 9and 9' is coupled rotatably to the bed 1. The other ends of the shaftsare fitted with bevel gears 13 and 13' engaged with bevel gears 12 and12' provided on a rotary shaft 11 coupled directly to a motor 10. Themotor 10 is supported by a support frame 18 projecting from the bed 1,and functions to move the moving unit transversely.

When the motor 10 is actuated, the front and rear screw shafts 9 and 9'are rotated synchronously so that the front and the rear sliders 7 and7' are slid parallel to each other in the direction of the width of thebed 1 at the same speed in the front and the rear guide grooves 8 and8'. At that time, the motor 10 can be rotated either forward or backwardto rotate the front and the rear screw shafts 9 and 9' forward orbackward to move the front and the rear sliders 7 and 7' forth or backat the same speed parallel to each other in the direction of the widthof the bed 1. A rotary encoder 20 is provided on the rotary shaft 11 atthe end thereof opposite the motor 10 so as to control the motor. Sincethe front and the rear sliders 7 and 7' thus are moved transversely, thefirst and second injection units 4a and 4b also are moved transverselyrelative to the stationary platen 5.

As shown in FIG. 3, a plurality of rear sliding shoes 14' are embeddedin the top of the rear slider 7' so as to enable the smooth swing of theswing plate 2. A plurality of front sliding shoes 14 are embedded in thebottom of the front portion of the swing plate 2 and positioned so thatthe shoes slide on the bed 1. A sliding rail 19 for guiding the swing ofthe swing plate 2 is provided on the bed 1 and located in a positioncorresponding to those of the front sliding shoes 14, to increase thestability of the swing plate at the time of the swing thereof. Acoupling mechanism (not shown) is provided to couple the swing plate 2and the front slider 7 to each other to move them together transversely,or to uncouple them from each other to swing only the swing plate.

FIG. 4 shows a positioning mechanism provided at the end of the frontslider 7 nearer the rotary shaft 11. The positioning mechanism includesa positioning metal portion 17 supported slidably by the front slider 7so as to be moved up and down by a piston rod 16' of a pneumaticcylinder 16, and three stop metal portions 21 (one being shown in FIG.4) secured to the bottom of the front guide groove 8 and correspondingto three molding positions described hereinafter. When the pneumaticcylinder 16 is actuated, the positioning metal portion 17 is moved downso that it is engaged with one of the three stop metal portions 21 so asto keep the transverse moving unit in one of the three molding positionswhich are a double injection molding position and two single injectionmolding positions located on either side of the double injection moldingposition.

Although the transverse moving unit includes the front and the rearsliders 7 and 7' fitted movably in the front and rear guide grooves 8and 8' of the bed 1, and also includes the swing plate 2 pivotallycoupled as a support structure for the rear slider 7' by the pivot pin6, in the embodiment described above, the unit is not so restricted inconstruction, but otherwise may be constituted to include a supportplate provided instead of the swing plate and secured to the front andthe rear sliders.

The transverse movement of the moving unit to the double and the singleinjection molding positions, in each of which molding is performed bythe injection molding machine, now will be described. The transversemoving unit can be moved to the double injection molding position inwhich the nozzles 11a and 11b of the first and the second injectionunits 4a and 4b are oriented to the two lateral nozzle insertion holes22a and 22c of the stationary platen 5. The moving unit also may bemoved to a first single injection molding position, in which the nozzle11a of the first injection unit 4a is oriented to the central nozzleinsertion hole 22b of the stationary platen 5, or a second singleinjection molding position, in which the nozzle 11b of the secondinjection unit 4b is oriented to the central nozzle insertion hole 22bof the stationary platen 5, as shown in FIG. 5. After the moving unit ismoved to a molding position, the unit is held there by a positioningmechanism.

To control the positioning mechanism, the position of the swing plate 2is detected by the rotary encoder 20 or by limit switches (not shown),and the pneumatic cylinder 16 is actuated in response to a detectionsignal from the encoder or the limit switches. If the motor 10 fortransverse movement of the moving unit is provided with a brake, therotation of the motor can be stopped instantly so as not to rotate thefront and the rear screw shafts 9 and 9', to move and stop the injectionunits 4a and 4b precisely in the molding positions in cooperation withthe setting of the positioning mechanism.

The steps of an injection molding method to be practiced with theinjection molding machine in accordance with the invention now will bedescribed. As the first injection unit 4a on the swing bearer 3a and thesecond injection unit 4b on the other swing bearer 3b remain moved back,the moving unit is moved transversely to the double injection moldingposition in which the nozzles 11a and 11b of the first and the secondinjection units are oriented to the two lateral nozzle insertion holes22a and 22c of the stationary platen 5, as shown in FIG. 5. Thepneumatic cylinder 16 shown in FIG. 4 then is actuated so that thepositioning metal portion 17 is moved down and the tip thereof isengaged in the corresponding stop metal portion 21 to position thetransverse moving unit. The first and second injection units 4a and 4bare moved forward thereafter on the swing bearers 3a and 3b so that thenozzles 11a and 11b of the injection units are inserted into the twolateral nozzle insertion holes 22a and 22c. After that, molten syntheticresins are injected from the first and second injection units 4a and 4binto dies having two gates. Double injection molding thus is performedby the injection molding machine.

As the first and the second injection units 4a and 4b remain moved back,the moving unit is moved transversely to one single injection moldingposition in which the nozzle 11a of the first injection unit 4a or thenozzle 11b of the second injection unit 4b is oriented to the centralnozzle insertion hole 22b of the stationary platen 5, as shown in FIG.5. The pneumatic cylinder 16 then is actuated so that the positioningmetal portion 17 is moved down and the tip thereof is engaged in thecorresponding stop metal portion 21 to position the moving unit. Thefirst or second injection unit 4a or 4b having its nozzle 11a or 11boriented to the central nozzle insertion hole 22b then is moved forwardso that the nozzle is inserted into the hole. Molten synthetic resinthereafter is injected from the injection unit into dies having a gate.Single injection molding thus is performed by the injection moldingmachine.

In an injection molding method provided in accordance with the presentinvention, first and second injection units are moved and positioned ina double injection molding position in which the nozzles of theinjection units are oriented to the two lateral nozzle insertion holesof a stationary platen, and double injection molding is performedthereafter. It also is possible that, in the inventive method, the firstand second injection units are moved and positioned in a singleinjection molding position in which the nozzle of one of the injectionunits is oriented to the central nozzle insertion hole of the stationaryplaten, and single injection molding is performed thereafter. Duringsingle injection molding, the injection unit not used therefor can besubjected to purging, flushing or the like, to greatly shorten the timeof preparation for a color change or material change, and can besubjected to maintenance work without downtime.

In addition to the foregoing, a double injection molding machineprovided in accordance with the present invention has the furtherdesirable effect that the first and second injection units of themachine can be moved easily and positioned in either of a doubleinjection molding position and a single injection molding position.

In addition, a double injection molding machine provided in accordancewith the present invention has a desirable effect in that a swing bearercan be swung in either of a double injection molding position and asingle injection molding position so as to perform fine adjustment bywhich the nozzles of the first and second injection units of the machineare aligned to the nozzle insertion holes of the stationary platen ofthe machine.

While the invention has been described in detail above with reference toa preferred embodiment, various modifications within the scope andspirit of the invention will be apparent to people of working skill inthis technological field. Thus, the invention should be considered aslimited only by the scope of the appended claims.

What is claimed is:
 1. A machine for performing both single and doubleinjection molding, comprising:a clamping unit having a stationary platenhaving three nozzle insertion holes, said holes being located at equalintervals in a horizontal row; a transverse moving unit, which is movedin a transverse direction parallel to said horizontal row; and twoinjection units positioned parallel to each other on support membersprovided on said moving unit; wherein said moving unit includes:drivemeans for moving said moving unit to a double injection molding positionin which the nozzles of said injection units are oriented with respectto two of the nozzle insertion holes, or to a single injection moldingposition in which the nozzle of one of said injection units is orientedto the central nozzle insertion hole; and a positioning mechanism forpositioning said moving unit in either of said single and doubleinjection molding positions.
 2. A machine according to claim 1, whereinthe support members comprise two swing bearers provided parallel to eachother on a swing plate pivotally coupled to the moving unit, so as toswing said injection units into said single and double moldingpositions.